The navigation problem of the ship lock is very important，but the serious sediment deposition will lead to the insufficient navigation depth of the channel and affect the navigation. In view of the problem of sediment deposition in the lower approach channel and entrance area of Qianwei ship lock，we use two-dimensional sediment model for numerical simulation，analyze the causes of sediment deposition，put forward and verify the measures of improving the channel sedimentation. The results show that affected the downstream riverbed topography and the boundary conditions of approach channel and entrance area，a wide range of backflow is formed，and the sediment deposition range and thickness are large. The sediment deposition is significantly reduced after taking the improvement measures.